Systems and methods herein generally relate to machines having print engines such as printers and/or copier devices and, more particularly, to printer color management in image/text printing.
The color gamut of a printer is a multi-dimensional space of a given volume with the axes of the space being set or defined initially by the pigments used in the colorants of the primary colors. Each set of color primaries: red, green, blue (RGB) or cyan, magenta, yellow, and black (CMYK), defines a “color space” that includes all colors that can result from any combination of these primaries. The “color space,” or “color gamut,” may be quite different for different sets of primaries. Typically, a CMYK color gamut is smaller than (although not completely within) an RGB color gamut, which means that the monitor can display more colors than a printer can print. In forming multi-color output images on an image-receiving medium, each of the primary colors is transferred to the image-receiving medium in turn. The color gamut is defined by the interaction of the primary colors, and is limited by a total amount of colorant in any combination that can be effectively deposited on the image-receiving medium. In other words, it is not possible to print some colors that can be photographed or displayed on a monitor when using CMYK printing. The color gamut for a particular image forming device and an associated color rendition dictionary (CRD) by which images may be produced by the image forming device is usually stored in metadata with the image forming device. The CRD and associated set of set points programmed into the image forming device, or family of image forming devices, ensures that the color gamut produced by that image forming device covers, as broadly as possible, an available standard color spectrum.
Some printers enable additional process colors for rendering an object. Such printers may include an additional housing (sometimes referred to as the fifth color housing, or Xth housing if more than 5 are enabled) that holds replaceable printing modules (sometimes referred to as a customer replaceable unit (CRU), fifth color module, spot color module, or imaging media cartridges) that are separate from the permanent color printing modules. This allows switching of the replaceable printing modules seamlessly in minutes; however, the fifth colorants are more expensive and used less frequently than the printer's permanent colors.
Extended gamut colorant destination profiles are designed to use the extended colorant in regions of the color space that cannot be rendered accurately by the main colors alone. The reason why the extended gamut colorant is used in these regions is to extend the printing gamut beyond the CMYK limitations.
Spot colors for printing are typically specially mixed inks that can be applied by an offset printing press. These specially mixed inks give a precise match to a designated color. Xerographic print devices do not have the ability to use the specialized inks and perform a best match with the CMYK colorants available. When a spot color is designated in a PDL (page description language) file, the Digital Front End (DFE) of the Xerographic print device consults a table of CMYK recipes (or a CIELAB value) for the best match possible. (The DFE is a component of the Xerographic print device that prepares and processes a job for the printer.) If a spot color name is not in the DFE table, an alternate color space value designated within the PDL is used. Each color typically has a CMYK recipe for an idealized printer (the CMYK colorants for a given print system vary, so the result of the same CMYK recipe on multiple print engine will vary in appearance).
Printing systems may also use specialty spots that are designated for colorants that cannot be reasonably mimicked using CMYK mixtures. These colorants include white, clear, and metallic, such as silver and gold. If these colorants are not available, the user does not want a CMYK facsimile of the color using the alternative color space designated within the PDL. Accordingly, there remains a need to provide a strategy to overcome the problem of undefined spot colors, within the DFE, in order to generate the user's desired image quality.